/* ==========================================
 * JGraphT : a free Java graph-theory library
 * ==========================================
 *
 * Project Info:  http://jgrapht.sourceforge.net/
 * Project Creator:  Barak Naveh (http://sourceforge.net/users/barak_naveh)
 *
 * (C) Copyright 2003-2006, by Barak Naveh and Contributors.
 *
 * This library is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation; either version 2.1 of the License, or
 * (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
 * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
 * License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this library; if not, write to the Free Software Foundation,
 * Inc.,
 * 59 Temple Place, Suite 330, Boston, MA 02111-1307, USA.
 */
/* -----------------
 * DefaultGraphMapping.java
 * -----------------
 * (C) Copyright 2005-2006, by Assaf Lehr and Contributors.
 *
 * Original Author:  Assaf Lehr
 * Contributor(s):   -
 *
 * $Id: DefaultGraphMapping.java,v 1.2 2007/05/22 15:52:53 kjellw Exp $
 *
 * Changes
 * -------
 */
package org.jgrapht.graph;

import java.util.*;

import org.jgrapht.*;

/**
 * Implementation of the GraphMapping interface. The performance of <code>
 * getVertex/EdgeCorrespondence</code>
 * is based on the performance of the concrete Map class which is passed in the
 * constructor. For example, using hashmaps will provide O(1) performence.
 * 
 * @author Assaf
 * @since Jul 30, 2005
 */
public class DefaultGraphMapping<V, E> implements GraphMapping<V, E> {
	// ~ Instance fields
	// --------------------------------------------------------

	private Map<V, V> graphMappingForward;

	private Map<V, V> graphMappingReverse;

	private Graph<V, E> graph1;

	private Graph<V, E> graph2;

	// ~ Constructors
	// -----------------------------------------------------------

	/**
	 * The maps themselves are used. There is no defensive-copy. Assumption: The
	 * key and value in the mappings are of valid graph objects. It is not
	 * checked.
	 * 
	 * @param g1ToG2
	 * @param g2ToG1
	 * @param g1
	 * @param g2
	 */
	public DefaultGraphMapping(Map<V, V> g1ToG2, Map<V, V> g2ToG1,
			Graph<V, E> g1, Graph<V, E> g2) {
		this.graph1 = g1;
		this.graph2 = g2;
		this.graphMappingForward = g1ToG2;
		this.graphMappingReverse = g2ToG1;
	}

	// ~ Methods
	// ----------------------------------------------------------------

	public E getEdgeCorrespondence(E currEdge, boolean forward) {
		Graph<V, E> sourceGraph, targetGraph;

		if (forward) {
			sourceGraph = this.graph1;
			targetGraph = this.graph2;
		} else {
			sourceGraph = this.graph2;
			targetGraph = this.graph1;
		}

		V mappedSourceVertex = getVertexCorrespondence(sourceGraph
				.getEdgeSource(currEdge), forward);
		V mappedTargetVertex = getVertexCorrespondence(sourceGraph
				.getEdgeTarget(currEdge), forward);
		if ((mappedSourceVertex == null) || (mappedTargetVertex == null)) {
			return null;
		} else {
			return targetGraph.getEdge(mappedSourceVertex, mappedTargetVertex);
		}
	}

	public V getVertexCorrespondence(V keyVertex, boolean forward) {
		Map<V, V> graphMapping;
		if (forward) {
			graphMapping = graphMappingForward;
		} else {
			graphMapping = graphMappingReverse;
		}

		return graphMapping.get(keyVertex);
	}
}

// End DefaultGraphMapping.java
